1. Field of the Invention
The present invention relates to a method of controlling an establishment of a multimedia call between at least two communication equipments, a corresponding system and a corresponding communication equipment. In particular, the present invention relates to method, system and communication equipment by means of which the set-up time for a video telephony call can be improved.
For the purpose of the present invention to be described herein below, it should be noted that                a communication equipment may for example be any device by means of which a user may access a communication network; this implies mobile as well as non-mobile devices and networks, independent of the technology platform on which they are based; only as an example, it is noted that communication equipments operated according to principles standardized by the 3rd Generation Partnership Project 3GPP and known for example as UMTS terminals are particularly suitable for being used in connection with the present invention;        although reference was made herein before to video telephony, this exemplifies only a specific example of content; content as used in the present invention is intended to mean multimedia data of at least one of audio data, video data, image data, text data, and meta data descriptive of attributes of the audio, video, image and/or text data, any combination thereof or even, alternatively or additionally, other data such as, as a further example, program code of an application program to be accessed/downloaded;        method steps likely to be implemented as software code portions and being run using a processor at one of the entities are software code independent and can be specified using any known or future developed programming language;        method steps and/or devices likely to be implemented as hardware components at one of the entities are hardware independent and can be implemented using any known or future developed hardware technology or any hybrids of these, such as MOS, CMOS, BiCMOS, ECL, TTL, etc, using for example ASIC components or DSP components, as an example;        generally, any method step is suitable to be implemented as software or by hardware without changing the idea of the present invention;        devices or means can be implemented as individual devices or means, but this does not exclude that they are implemented in a distributed fashion throughout the system, as long as the functionality of the device is preserved.        
2. Related Prior Art
In the last years, an increasingly extension of communication networks, e.g. of wire based communication networks, such as the Integrated Services Digital Network (ISDN), or wireless communication networks, such as the cdma2000 (code division multiple access) system, cellular 3rd generation (3G) communication networks like the Universal Mobile Telecommunications System (UMTS), cellular 2nd generation (2G) communication networks like the Global System for Mobile communications (GSM), the General Packet Radio System (GPRS), the Enhanced Data Rates for Global Evolutions (EDGE), or other wireless communication system, such as the Wireless Local Area Network (WLAN), took place all over the world. Various organizations, such as the 3rd Generation Partnership Project (3GPP), the International Telecommunication Union (ITU), 3rd Generation Partnership Project 2 (3GPP2), Internet Engineering Task Force (IETF), and the like are working on standards for telecommunication network and multiple access environments.
In general, the system structure of a communication network is such that one party, e.g. a subscriber's communication equipment, such as a mobile station, a mobile phone, a fixed phone, a personal computer (PC), a laptop, a personal digital assistant (PDA) or the like, is connected via transceivers and interfaces, such as an air interface, a wired interface or the like, to an access network subsystem. The access network subsystem controls the communication connection to and from the communication equipment and is connected via an interface to a corresponding core or backbone network subsystem. The core (or backbone) network subsystem switches the data transmitted via the communication connection to a destination party, such as another communication equipment, a service provider (server/proxy), or another communication network. It is to be noted that the core network subsystem may be connected to a plurality of access network subsystems. Depending on the used communication network, the actual network structure may vary, as known for those skilled in the art and defined in respective specifications, for example, for UMTS, GSM and the like.
Generally, for properly establishing and handling a communication connection between network elements such as the communication equipment and another communication equipment or terminal, a database, a server, etc., one or more intermediate network elements such as control network elements, support nodes or service nodes are involved.
One application whose importance for current and future communication systems increases are multimedia communication services, and in particular conversational video telephony (VT) services. Generally, video communication is related to a communication with moving pictures, but it also to some extent concerns text and voice, especially in combination for multimedia communication or calls. A multimedia call is a communication where, for example, sound (voice), text and picture are used simultaneously. Video telephony, also called videophone, is defined as remote communication via terminals, capable of transmitting substantially in real time moving pictures and audio between a sender and a receiver reciprocally. Since such conversational VT services are delay sensitive applications, as a delay during the transmission of a VT call is incommoding and inconvenient for a user, it is required to chose adequate signalling paths and procedures for VT calls in order to ensure that the quality of such a connection is sufficient for the user. Furthermore, since VT call requires the transmission of several different types of data (video, audio, and the like) in parallel, and these data are to be transmitted and received by various different types of communication equipments or network elements, it is required that plural communication protocols are negotiated and appropriate parameters for the communication are adjusted.
For example, in 3G networks, it is mandated by the 3GPP to use a 3G bandwidth guaranteed circuit switched bearer. Furthermore, as the standard to be used for such a multimedia communication, a 3G-324M system is to be employed. The 3G-324M system represents a derivate of the ITU-T H.324 protocol which in turn requires the employment of several further components or protocols, such as the ITU-T H.223 protocol for multiplex and the ITU-T H.245 protocol for call control for multimedia communications between different multimedia systems. The general procedures for establishing a multimedia communication are known for those skilled in the art so that a detailed description thereof is omitted herein.
Generally, when a multimedia call like a VT call is to be established, for example in a 3G network using the 3G-324M system mentioned above, the following (simplified described) procedures are executed. Further details of these procedures can be found, for example, in 3GPP specifications TS 26.112 V1.1.0, TS 24.008 V3.16.0, and TR 26.911 V3.4.0.
The negotiation of parameters for the VT call is done in following phases:                A: In a first signalling phase, BCIE (Bearer Capability Information Element) and LCIE (Low layer Compatibility Information Element) parameters are exchanged. This is the normal mobile call setup procedure, as executed, for example in voice and data calls. The BCIE and LCIE parameters inform the other entity (i.e. another communication equipment) of the bearer capabilities of the peer end (i.e. the (calling) communication equipment) and is primarily used to setup the bearer link (i.e. a physical layer connection). Once the physical link is established, a bearer protocol starts sending stuffing information into the just created bit pipe. The actual video protocol data is provided to the bit pipe by a video application protocol, once it has been initialized.        B: In an application protocol negotiation phase, the application protocol is initialized and a application protocol “handshaking” procedure is started with the peer entity. This phase takes normally much longer than phase A. It is to be noted that the handshaking of application protocol parameters is not possible before the physical bit pipe has been created.        
In such a conventional video call establishment, the setup time may last a comparative long time. The reason for this is, as mentioned above, that such a video call setup requires several level of protocol negotiation in order to exchange and agree the video application parameters between peer entity (i.e. communication equipments participating in the video call). However, long waiting times before the video call can actually be started are undesired and lower the attractiveness of video telephony services for the users.
Presently, there are proposed various proprietary solutions to speed up the video call setup. However, those solutions are related to speed up video protocol negotiation. For example, vendor ID information are used to select parameters for the logical channel to be proposed.